Greenhouse and field experiments were conducted to evaluate the response of okra to different levels of human urine (0, 10,000, 15,000 and 20,000 L/ha) and 400 kg/ha NPK 15:15:15 inorganic fertilizer in five riverine communities of Cross River State, Nigeria. The soils of the communities are generally acid with low organic matter, total nitrogen, exchangeable cations, but were rated medium in available P. The pH of the urine was alkaline with moderate amount of nutrients. There was a significant (P < 0.05) increase in nutrient uptake with application of either urine or inorganic fertilizer compared with the control. Application level of 20,000 L urine/ha significantly increased the growth and yield attributes of okra plants relative to NPK fertilizer, while 15,000 L urine/ha had a similar effect on okra plant as the inorganic fertilizer. The inert potentials of human urine as a good source of organic fertilizer are discussed.

http://dx.doi.org/10.1016/j.resconrec.2012.02.003

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The mobility and bioavailability of cadmium, copper, lead and zinc were evaluated in three soils amended with different organic materials for two moisture regimes. Agricultural and reclamation activities impose fresh inputs of organic matter on soil while intensive irrigation and rainstorm increase soil waterlogging incidence. Moreover, scarcity of irrigation water has prompted the use of greywater, which contain variable concentrations of organic compounds such as anionic surfactants.

Soils added with hay, maize straw or peat at 1% w/w were irrigated, at field capacity (FC) or saturated (S), with an aqueous solution of the anionic surfactant Aerosol 22 (A22), corresponding to an addition of 200 mg C/kg soil/day. Soil solution was extracted after one month and analysed for total soluble metals, dissolved soil organic matter and UV absorbance at 254 nm. Speciation analyses were performed with WHAM VI for Cd, Cu, Pb, and Zn. For selected scenarios, metal uptake by barley was determined.

Metal mobility increased for all treatments and soils (Pb > Cu > Cd ≥ Zn) compared to control assays. The increase was significantly correlated (p < 0.05) with soil organic matter solubilisation for Cd (R = 0.68), Cu (R = 0.73) and Zn (R = 0.86). Otherwise, Pb release was related to aluminium solubilisation (R = 0.75), which suggests that Pb was originally co-precipitated with Al–DOC complexes in the solid phase. The effect of A22 in metal bioavailability, determined as free ion activities (FIA), was mainly controlled by soil moisture regime. For soil 3, metal bioavailability was up to 20 times lower for soil amended with hay, peat or maize compared to soil treated only with A22. When soil was treated with A22 at FC barley yield significantly decreased (p < 0.05) for the increase of Pb (R = 0.71) and Zn (R = 0.79) concentrations in shoot, while for saturated conditions such uptake was up to 3 times lower.Overall, metal bioavailability was controlled by solubilisation of soil organic matter and formation of metal-organo complexes.

http://dx.doi.org/10.1016/j.scitotenv.2012.02.033

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Approaches to reduce N2O emission from crop ecosystems deserves urgent need for climate change mitigation in world agriculture. Yet, unique ecological measures to depress N emission while conserving crop productivity have not yet been well developed for wide ranges of crop ecosystems. In order to establish an ecological engineering option to mitigate N2O emission in rice ecosystems, we conducted a field experiment with biochar amendment on N2O emission from rice paddies in three sites across South China in 2010. This experiment was performed with 6 treatments of biochar rates of 0, 20, and 40 t ha−1 with and without N fertilization respectively. The rice ecosystem was managed with conventional crop production practices as seasonally man-managed wetlands, which were under flooding after seedling transplantation till panicling and drainage during spiking followed by a subsequent moist condition (F-D-M) till harvest across sites. Emission of N2O from rice soil was monitored with closed chambers at 7 days interval throughout the whole rice growing season (WRGS) and the gas samples analyzed with a gas chromatograph (Agilent 7890D) equipped with an electron capture detector (ECD). Total emission of N2O-N ranged from 1.5 kg N2O-N ha−1 to 1.9 kg N2O-N ha−1 without biochar, and from 0.8 kg N2O-N ha−1 to 1.3 kg N2O-N ha−1 and from 0.7 kg N2O-N ha−1 to 0.9 kg N2O-N ha−1 with biochar amendment at 20 t ha−1 and 40 t ha−1, respectively. Thus, biochar amendment depressed total N2O emission from chemical N fertilizer, as the calculated EF of N2O-N emission was reduced from 0.57 ± 0.15% under chemical N fertilizer only to 0.36 ± 0.08% and 0.22 ± 0.04% under biochar amendment at 20 t ha−1 and 40 t ha−1 respectively. The value under biochar amendment at 40 t ha−1 was found even much smaller than that of a continuously flooding rice ecosystem. As soil pH (H2O), content of soil organic carbon and total N were all upraised significantly, biochar amendment improved rice ecosystem functioning by decreasing N2O-N emission per metric ton of rice production from 0.17 ± 0.02 kg N2O-N without biochar to 0.10 ± 0.02 and 0.07 ± 0.03 kg N2O-N under biochar respectively at 20 t ha−1 and 40 t ha−1. Thus, soil amendment of biochar from crop straw could be adopted as a unique ecological engineering measure to reduce N2O emission while enhancing soil fertility and sustaining rice productivity in rice ecosystems.

http://dx.doi.org/10.1016/j.ecoleng.2012.01.016

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After presenting a general overview of the soil quality concept, we review the existing LCA approaches that consider soil quality in their inventory and impact-assessment phases, and outline the challenges to refining soil quality impacts in LCA. These challenges include estimation of complex soil quality impacts that depend on fluctuating soil characteristics, consideration of both on-site and off-site agricultural soils, and aggregation of impacts both spatially and temporally. The inventory items describing soil quality can be soil properties, functions or processes (e.g., erosion, compaction). Their quantification implies that they be (1) relevant for calculating impacts on soil quality, (2) related to one or more functional units, (3) as accurate as possible and (4) calculated with available data at a global scale. Inventory items based on processes fulfill these four needs and can be considered as midpoint indicators in LCA. Furthermore, indicators based on processes allow an incremental improvement of the method through the inclusion of new impacts. Efforts first must focus on developing robust impact indicators for individual soil processes before attempting to aggregate them into a single indicator. Nonetheless, several aggregation approaches are presented. The appropriate level of complexity and comprehensiveness for assessing impacts on soil quality should result from a compromise between oversimplified and overcomplicated descriptions of the multiple functions and properties of soils.

http://dx.doi.org/10.1016/j.ecolind.2011.12.014

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Carbon Terra – home

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DOI: http://dx.doi.org/10.1016/j.agee.2011.12.010

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